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Re: Problem with Async (multiple) notifications

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andres Olarte <olarte(dot)andres(at)gmail(dot)com>
Cc: pgsql-jdbc(at)postgresql(dot)org
Subject: Re: Problem with Async (multiple) notifications
Date: 2005-06-25 04:14:25
Message-ID: 17989.1119672865@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-jdbc
Andres Olarte <olarte(dot)andres(at)gmail(dot)com> writes:
> I've been playing with async notifications lately, and I've found a
> small problem: when several notifications are issued at once (for
> example within a transaction) normally only one of those gets to the
> client.

The documentation:
http://www.postgresql.org/docs/8.0/static/sql-notify.html
quoth:
> NOTIFY behaves like Unix signals in one important respect: if the same
> notification name is signaled multiple times in quick succession,
> recipients may get only one notification event for several executions of
> NOTIFY. So it is a bad idea to depend on the number of notifications
> received. Instead, use NOTIFY to wake up applications that need to pay
> attention to something, and use a database object (such as a sequence)
> to keep track of what happened or how many times it happened.

Are you sure you are following this advice?

(In particular, I can absolutely positively guarantee that N NOTIFYs
executed within a single transaction have the same effect as one
NOTIFY.  This is not a bug, it is the design intention.)

			regards, tom lane

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